I've installed Zimbra a few times previously and have never had any problems until now.

Were these installs done on RHEL6 ? This may be the cause of your problems. Not because there's anything wrong with RHEL6, but because the packaged Zimbra installer was not made for it.

A while back I tried to install Zimbra Community Ed. for Fedora 11 (if memory serves) on a Fedora 12 machine and it failed. This was because of some Perl library, that came with this new distro, that was incompatible with the packaged ZCS.

Besides the LDAP error messages are you seeing anything in the install log?

Besides the LDAP error messages are you seeing anything in the install log?

Everything after the errors I listed above in my first post failed from that point... because the lack of LDAP being configured properly is my assumption. That's why I focused on those errors.

I tried another time with a fresh install. (following my own wiki article that I created upon a successful install a few months ago) The second attempt produced the same errors. I've wiped the OS and am going to move to another project for now.

I hope when I get back to this the next time I will have some leads to go on!

Using configuration from /opt/zimbra/ssl/zimbra/ca/zmssl.cnf
unable to load number from /opt/zimbra/ssl/zimbra/ca/ca.srl
error while loading serial number
26907:error:0D066091:asn1 encoding routines:a2i_ASN1_INTEGERdd number of chars:f_int.c:162: